Regenerated cellulose-polyethylene glycol high fluid-holding fiber mass

ABSTRACT

1. FLUID ABSORBENT ALLOY FIBERS COMPRISED OF A MATRIX OF REGENERATED CELLULOSE HAVING UNIFORMLY DISPERSED THEREIN FROM ABOUT 5 TO ABOUT 25%, BASED UPON THE WEIGHT OF THE CELLULOSE, POLYETHYLENE GLYCOL HAVING A MOLECULAR WEIGHT WITHIN THE RANGE OF FROM 10,000 TO 40,000.

United States Patent 3,843,378 REGENERATED CELLULOSE-POLYETIIYLENE GLYCOL HIGH FLUlD-HOLDIN G FIBER MASS Frederick R. Smith, Wilmington, Del., assignor to FMC Corporation, Philadelphia, Pa. No Drawing. Filed Oct. 16, 1972, Ser. No. 298,029 Int. Cl. A61f 13/20; C08b 23/00; C08g 43/02; D01f 3/14 US. Cl. 106-168 7 Claims ABSTRACT OF THE DISCLOSURE Alloy fibers having high fluid-holding capacity, and a method for making the same, the alloy fibers being comprised of regenerated cellulose having a uniform dispersion of normally solid polyethylene glycol therein.

The present invention is directed to alloy fibers having high fluid-holding capacity.

Alloy fibers consisting of sodium carboxymethyl cellulose and regenerated cellulose have been employed in various articles which are intended to absorb body liquids. While the fluid-holding capacity of these alloy fibers is greater than that of conventional regenerated cellulose fibers, this advantage is at least partially offset by their higher manufacturing costs.

One mode of making such known alloy fibers involves the mixing of sodium carboxymethyl cellulose into viscose and then converting this mixture into fibers using the conventional viscose spinning system. Drying of the resulting alloy fibers to cardable form is difiicult. This ob jective can be attained, however, by treating the alloy fibers with special finishes, removing Water therefrom with alcohol, and then finally drying the alcohol-wet fibers. Aside from introducing greater complexity into the manufacturing process, the finishing and drying of the alloy fibers by solvent exchange is a relatively costly procedure. Accordingly, a primary object is to provide new or generally improved and more satisfactory absorbent alloy fibers and a method for making the same.

Another object of this invention is to provide absorbent alloy fibers of regenerated cellulose containing a uniform dispersion of polyethylene glycol.

Still another object is the provision of a method for making absorbent alloy fibers from a mixture of viscose and polyethylene glycol in which no special finishes and/ or drying procedures are required.

These and other objects are accomplished in accordance with the present invention by absorbent alloy fibers, each having a matrix of regenerated cellulose and a normally solid polyethylene glycol uniformly dispersed therein, with the regenerated cellulose being the major portion of the fiber mass.

As employed throughout the description and claims, the terminology alloy fibers refers to cellulose fibers having polyethylene glycol contained therein. Similarly fluid-holding capacity is a measure of liquid absorbed into the fibers of a mass of alloy fibers together with the liquid retained within the interstices of such fiber mass.

Unless otherwise indicated, the amounts of polyethylene glycol employed are set forth as percentages based upon the weight of the cellulose in the viscose.

The alloy fibers of the present invention are prepared by mixing an aqueous solution of a normally solid polyethylene glycol with a filament-forming viscose, shaping the mixture into fibers, coagulating: and regenerating the shaped fibers and thereafter drying the same. Viscose constitutes the major portion of the mixture and the shaped alloy fibers are coagulated and regenerated by known means, and preferably in an acid bath containing sulfuric acid and sodium sulfate. Zinc sulfate is often incorporated in the bath as well as other coagulation modifiers, as desired. No special finishes and/or drying procedures are required to render the alloy fibers in a form which can be carded without difiiculty.

The viscose which is employed in making the alloy fibers of the present invention is, desirably, of a composition as is used in making conventional regenerated cellulose fibers. The composition of such viscose is Well documented in the prior art and, in general, is produced by reacting alkali cellulose with carbon disulfide, with the resulting sodium cellulose xanthate being diluted with aqueous caustic to provide the resulting viscose with a desired cellulose and alkali content. Additives or modifiers may be mixed in the viscose if desired.

The polyethylene glycols which are suitable for use in the present invention are normally solid, having molecular weights ranging from about 10,000 to about 40,000. Such polyethylene glycols are manufactured by procedures which are well known in the art as by the hydration of ethylene oxide, and are commercially available, for example, as Carbowax compounds.

In the manufacture of conventional regenerated cellulose fibers, it has not been uncommon to employ polyethylene glycols as spinning assistants in viscose coagulating baths to prevent the encrustation of spinnerets. For example, US. Pat. No. 2,324,437 teaches that, based upon the total weight of a coagulating bath, from 0.001% to 1.0% of polymerized ethylene oxide (Carbowax 4000) may be incorporated into such bath to assist in inhibiting spinneret cratering.

In accordance with the present: invention, however, polyethylene glycol is incorporated directly into a viscose and is employed in relatively large quantities, ranging from about 5% to about 45%, and particularly from 30 to 45%, based upon the weight of the cellulose in the viscose. Fibers formed from a viscose containing less than about 5% of polyethylene glycol do not differ appreciably from conventional regenerated cellulose fibers in their fluid-holding capacity. Increasing the amount of polyethylene glycol in the viscose above the range specified generally results in a very significant decrease in the denier of the alloy fibers which are produced, thus indieating that the increased amounts of polyethylene glycol are poorly retained.

The normally solid polyethylene glycols described exhibit good solubility in water and, in accordance with the method of the present invention, aqueous solutions of the polyethylene glycols are injected into the viscose as it is pumped to spinnerets for extrusion. Alternatively, aqueous solutions of polyethylene glycols and viscose may be passed through a blender or homogenizer if it is necessary to secure a more uniform dispersion. After spinning, coagulation, and regeneration stages, the shaped continuous tow of filaments undergoes the usual processing, which may include stretching if desired, and then dried by conventional means. Generally, before drying the continuous tow of filaments is cut into staple of a desired length. The resulting alloy fibers contain from 5 to 25% of polyethylene glycol, based upon the weight of the cellulose in the fibers. In view of the lubricity imparted to the alloy fibers by such contained polyethylene glycol, the resulting alloy fibers experience no bonding during drying and can be subsequently carded with no difliculty by the manufacturer of articles incorporating such fibers.

The alloy fibers of the present invention are adapted for use in a variety of articles, such as tampons, in which fluid retention is an essential characteristic. In the manufacture of such articles, the alloy fibers necessitate no special techniques or equipment and they may be blended with other fibers which may or may not enhance the absorbent properties of the resulting articles. Fibers with which the alloy fibers of the present invention may be blended include, for example, rayon, cotton, chemically modified rayon or cotton, cellulose acetate, nylon, polyester, acrylic, polyolefin, etc.

The fluid-holding capacity of the alloy fibers of the present invention was determined by a procedure, as follows:

Sample staple alloy fibers are carded or otherwise well opened and then conditioned. Two grams of such alloy fibers are placed in a one-inch diameter die, pressed to a thickness of 0.127 inch, and maintained in this condition for one minute. This compressed pellet of alloy fibers was removed from the die and placed on a porous plate of a Biichner funnel. The upper surface of the pellet was then engaged with a plunger which was mounted for free vertical movement, the plunger having a diameter of one inch and a weight of 2.4 pounds.

The funnel stern was connected by a flexible hose to a dropping bottle from which water was introduced into the funnel to wet the pellet of alloy fibers. Control over the water flow was exercised by the position of the dropping bottle. After an immersion period of two minutes, the water was permitted to drain from the alloy fiber pellet for three minutes, after which the still wet pellet was removed from the funnel and weighed. One-half of the weight of water in the sample pellet is a measure of the fluid-holding capacity of the alloy fibers, expressed in cc./g.

The following example is provided to further demonstrate the merits of the present invention.v

EXAMPLE Using conventional spinning equipment, aqueous solutions of polyethylene glycol having a molecular weight of about 20,000, Polyethylene Glycol Compound M, were injected by metering pump into a viscose stream during its passage through a blender and immediately prior to its extrusion. The viscose composition was 9.0 cellulose, 6.0 sodium hydroxide and 32% carbon disulfide, based upon the weight of the cellulose. The viscose ball fall was 56 and its common salt test was 7.

The mixtures of viscose and polyethylene glycol were extruded through 720 hole spinneret into an aqueous spinning bath consisting of 7.5% by weight of sulfuric acid, 18% by weight of sodium sulfate, and 3.5 by weight of zinc sulfate. After passage through the spinning bath, the resulting continuous tow was washed with water, desulfurized, and again washed with water. The still wet tow was cut into staple fibers which were without any further treatment, dried, conditioned and then carded.

The fluid-holding capacity of sample alloy fibers containing different amounts of polyethylene glycol was determined using the above-described test procedure. The results of such were as follows:

Fluid-holding capacity Percent Percent Percent PE G PE G 1 Ce./g. increase retained 2 l Polyethylene glycol injected, based upon the weight of the cellulose in the viscose. figeljsercentages of injected polyethylene glycol retained by finished From the above data it is apparent that the alloy fibers of the present invention exhibit fluid-holding capacities which exceed those of conventional regenerated cellulose fibers, and that at concentrations exceeding 45%, reduced retention of the injected polyethylene glycol is experienced.

I claim:

1. Fluid absorbent alloy fibers comprised of a matrix of regenerated cellulose having uniformly dispersed therein from about 5 to about 25%, based upon the weight of the cellulose, polyethylene glycol having a molecular weight within the range of from 10,000 to 40,000.

2. Fluid absorbent alloy fibers as defined in claim 1 wherein the polyethylene glycol has a molecular weight of about 20,000.

3. Fluid absorbent alloy fibers as defined in claim 1 shaped into the form of a tampon.

4. A method of making fluid absorbent alloy fibers comprising mixing into a filament-forming viscose an aqueous solution of polyethylene glycol having a molecular weight within the range of from 10,000 to 40,000 to incorporate into such viscose, based upon the weight of the cellulose therein, from 5 to 45% of the polyethylene glycol, shaping the mixture into fibers, coagulating and regenerating the shaped fibers and thereafter drying the fibers.

5. A method as defined in claim 4 wherein the polyethylene glycol is present in the viscose in an amount ranging from 30 to 45 based upon the weight of the cellulose in the viscose.

6. A method as defined in claim 4 wherein the polyethylene glycol has a molecular weight of about 20,000.

7. A method as defined in claim 5 wherein the polyethylene glycol has a molecular weight of about 20,000.

References Cited UNITED STATES PATENTS 3,182,107 5/1965 Howsmon et al 264l93 3,664,343 5/1972 Assarsson 128-284 3,423,167 1/1969 Kuzmak et al 264191 3,434,913 3/1969 Bockno et a1 264l93 FOREIGN PATENTS 808,838 2/1959 Great Britain 264l93 1,069,498 5/1967 Great Britain 264l93 WILLIAM H. SHORT, Primary Examiner E. WOODBERRY, Assistant Examiner US. Cl. X.R. 

1. FLUID ABSORBENT ALLOY FIBERS COMPRISED OF A MATRIX OF REGENERATED CELLULOSE HAVING UNIFORMLY DISPERSED THEREIN FROM ABOUT 5 TO ABOUT 25%, BASED UPON THE WEIGHT OF THE CELLULOSE, POLYETHYLENE GLYCOL HAVING A MOLECULAR WEIGHT WITHIN THE RANGE OF FROM 10,000 TO 40,000. 